Set Coefs Page

The Set Coefs page is used for entering forced values and for excluding coefficients from the fitting procedure. This page belongs to the 1-D Fit Preferences dialog. Values set on this page are assigned to the fit coefficients only if the check box is checked beside the button on the 1-D Fit Toolbar. Also see an example of coefficient forcing at work.

Forcing Coefficient Values

A forced coefficient is assigned a value and is not estimated by the fit. The value is used in the fit and does affect the outcome of the other, non-forced coefficients. A forced coefficient is listed in the 1-D Fit Messages window like this:

     Coef[1]*= 0.0 (forced)

using whatever value you assigned to it. The * left of the = sign means "forced". The uncertainty (error value) of a forced coefficient is not listed, since it is identically 0 because it was not estimated by the fit.

Procedure

To force one of more coefficients to have a specific value, you must do two things: 1) Specify values and check boxes in the Force column on the Set Coefs page, and 2) enable forcing on the 1-D Fit Toolbar:

1. For each coefficient to set:

2.     Enter the value into the table.

       Check the checkbox to use the value. [more] If a checkbox is un-checked, it does not matter that a value is entered for the coefficient. This allows the table to remain populated even though the coefficients may not be used.

3. Click [Apply] or [OK] to save your changes.

4. On the 1-D Fit Toolbar, enable or disable coefficient forcing using the checkbox:

Enable forcing by checking the checkbox next to the button.

Disable forcing using one of these methods:

    To disable all forced coefficients, un-check the button on the 1-D Fit Toolbar.

    To de-activate a coefficient, un-check its checkbox on the Set Coefs page.

    To deactivate all forced coefficients, uncheck all of their boxes on the Set Coefs page. An easier method is to use on the toolbar.

Notes:

• Forced Values may be held in the table but not activated unless their checkbox is checked.

• Coefficient forcing can be activated directly from the 1-D Fit Toolbar.

How to Exclude an Order from the Fit

To exclude an order from the fit, simply set its value to 0.0 and follow the procedure given above. For example, to exclude the linear term, Coef[1], from the fit shown in the dialog above, do this:

1. In the Set Coefs dialog, set the value of Coef [1] to 0.0 and check the box beside it.

2. Click [OK] to save your changes and dismiss the dialog.

3. On the 1-D Fit Toolbar, enable forcing by checking .

When you calculate a new fit, the value of Coef[1] will be listed like this:

     Coef[2]*= 0.25 (forced)

Related Topics

1-D Fit Package, 1-D Fit Toolbar, Example